This invention relates to improvements in clamp mechanisms for use in securing a steering column shroud in position within a vehicle.
It is known to provide a steering column assembly for a vehicle which comprises a steering column shaft supported by one or more bearings within a shroud. The shaft connects a steering wheel at one end to the road wheels of the vehicle, usually through a steering rack. The shroud is fixed to the vehicle through a support bracket. To enable the steering to be adjusted for rake (or height) the shroud is often movable relative to the support bracket, with a clamp mechanism being provided that in a clamped position prevents movement of the shroud relative to the bracket. The shroud is also, in some cases, adjustable for reach by allowing one part of the shroud to move telescopically relative to another. The same clamp mechanism that secures the shroud to the bracket usually also prevents the shroud from being adjusted for reach when in the clamped position.
Many forms of clamp mechanism are known in the art. In one arrangement an elongate clamp pin passes through a slot in the bracket and a slot in the shroud, the pin having fixed or adjustable end stops, or reaction members, at each end to define a fixed length of pin between them. A cam mechanism which is adjustable for length is located on the pin between one of the ends stops and the part of the bracket with the slot. When the cam mechanism is at its shortest length the bracket is only loosely connected to the shroud allowing the shroud to be moved relative to the bracket. When it is at its longest length the bracket and shroud are clamped together as the cam mechanism pushes against the end stop and bracket, so the shroud cannot move relative to the bracket.
The cam mechanism is operated by a lever. Rotation of the lever rotates a part of the cam mechanism which converts that movement into the linear movement associated with a change in length. To move the bracket and shroud apart when unclamped, a spring is provided. This spring applies a force to the bracket arm which can in some cases move the cam rapidly to the end of its travel where movement will come to an abrupt stop.